Stability of plane poiseuille flow of a highly elastic liquid

The stability of fully developed pressure driven plane laminar flow of a Maxwell fluid has been studied using linear hydrodynamic stability theory. Elasticity is destabilizing in the inertial regime, but the flow is found to be stable to infinitesimal disturbances at low Reynolds numbers. This result contradicts previous calculations, which predicted a low Reynolds number flow instability at a critical recoverable shear of order unity. The previous calculations were carried out using less accurate numerical methods; the eigenvalue problem which must be solved is a delicate one, requiring sophisticated umerical techniques in order to avoid the calculation of spurious unstable modes.This work has direct bearing on the question of the mechanism of a low Reynolds number extrusion instability known as “melt fracture”. It is observed that the intensity of melt fracture increases with increasing die length for high density polyethylene, and it is therfore believed by some experimentalists that fully-developed die flow is unstable for this polymer above a critical recoverable shear. The analysis appears to be at variance with this interpretation of the experimental results.     

Estimation of the degree of fusion of rigid PVC from thermal analysis measurements

PVC that has been processed exhibits two endothermic peaks in DSC heating curves. These endotherms are separated by a temperature. Tc, which is characteristic of the maximum temperature reached in prior processing. The relative value of the lower temperature endotherm has been proposed as a measure of degree of gelation of unplasticized PVC. This measure is not exact, however, because it does not reflect the extent of breakdown of primary PVC particles. An alternative DSC measurement technique is proposed that reflects the degree of fusion more accurately. The nature of the various endotherms that are observed is a subject of speculation in this article.     

The vibrations of generally orthotropic beams,a finite element approach

This paper presents two finite element models for the prediction of free vibrational natural frequencies of fixed-free beams of general orthotropy. The discrete models include the transverse shear deformation effect and the rotary inertia effect. Numerical studies show that the convergence rate of the approximations calculated from the finite element analysis is dependent on the fibre orientation.     

The effects of fibre orientation on free vibrations of composite beams

The torsion-flexure coupling effect of generally orthotropic beams is dependent on reinforcing fibre orientation and mode order. At higher ranks of vibration, this coupling effect is principally contributed by the twisting moment induced by bending. The influence of fibre orientation on normal mode shapes is more significant for small values of fibre orientation. The mode shapes can change suddenly with a small increase in fibre orientation.     

Masses of S and P wave mesons and pseudoscalar decay constants using a confinement scheme

In the framework of relativistic harmonic confinement model for quarks and antiquarks, the masses of S- and P-wave mesons and pseudoscalar decay constants from light flavour to heavy flavour sectors are computed. The residual two-body Coulomb interaction and the spin-dependent interaction of the confined one gluon exchange effects (COGEP) such as spin-spin and spin-orbit interactions are perturbatively incorporated with the confinement energy to get the respective vector-pseudoscalar meson mass differences. Here we employ the same parametrization and model parameters as used in a recent study of low-lying hadron masses and leptonic decay widths. The results are being compared with the values obtained from other theoretical models and the experimental values.